1. Field of the Invention
This invention relates to an electronic part in which a circuit element is mounted on the major surface of a printed circuit board, dielectric filter, dielectric duplexer, and manufacturing method of the electronic part.
2. Description of the Related Art
Up to now, in an electronic part where a plurality of chip parts, etc. are put together into a component which functions as a fixed circuit, circuit elements of chip-like elements and others are mounted on the upper surface (first major surface) of a printed circuit board and terminal electrodes are formed on the lower surface (second major surface) of the printed circuit board.
For example, when one dielectric duplexer is constructed of a plurality of coaxial dielectric resonators, terminal Tx to input a transmission signal from a transmission circuit, terminal Rx to output a reception signal to a reception circuit, terminal ANT to connect an antenna, and others are provided on the lower surface of a printed circuit board, chip capacitors and coils are mounted together with a plurality of coaxial dielectric resonators on the upper surface on the printed circuit board, and a shield cover is set in the upper part.
FIG. 10 is a sectional view of a terminal electrode in the above conventional electronic part. However, the hatching or the like indicating the section is omitted in order to show the drawing clearly. In FIG. 10, reference numeral 1 represents the base material of a printed circuit board. At a fixed location of the base material 1, a terminal electrode is provided in such a way that the main part of the terminal electrode is constructed of a copper foil 21, that a soldering-resistant film 3 is formed in a portion not to be soldered, and that further a plated upper film 23 is formed at a location to be soldered.
However, an electronic part where circuit elements are mounted on a printed circuit board as in the above, has the property that the printed circuit board itself is warped and that the whole printed circuit board is likely to get warped and distorted when the circuit element is mounted on the upper surface of the board by soldering, etc. Therefore, when the above electronic part is mounted on a circuit board of electronic equipment, there was a possibility that a gap is caused between the lower surface of the printed circuit board of the electronic part and the upper surface of the circuit board of electronic equipment and reliable connection may not be performed between the terminal electrodes.
FIG. 11 shows one example of such cases. In FIG. 11, a circuit board 4 of electronic equipment is shown and a terminal electrode 5 is formed on the upper surface of the circuit board. Generally, the terminal electrode 5 of the circuit board is composed of 80 to 150 xcexcm thick printed solder, and as a soldering-resistant film 3 is protruded about 20 xcexcm from a terminal electrode 2 the terminal electrode 2 of the printed circuit board and the electrode 5 of the circuit board make contact with each other. However, as shown in FIG. 11, when the end portion of the printed circuit board 1 is warped so as to leave from the circuit board 4, the terminal electrode 2 of the printed circuit board is lifted out of the terminal electrode 5 of the circuit board which is likely to cause soldering defects.
Furthermore, it is possible to mount electronic parts on the circuit board of electronic equipment by making use of solder bumps formed on the lower surface of a printed circuit board of electronic part, but because of the solder bumps which are about 0.3 to 0.5 mm high a relatively large gap is caused between the printed circuit board and the circuit board 4. Therefore, particularly in the electronic parts such as filters in high-frequency circuits, there was a possibility that such a problem that signals are likely to couple between input-output terminals, that once coupled their attenuation characteristics are deteriorated, and that fixed characteristics cannot be realized after the mounting on the circuit board of electronic equipment is caused.
To overcome the above described problems, preferred embodiments of the present invention provide an electronic part in which even if the printed circuit board of the electronic part is warped or distorted reliable connection takes place between the terminal electrodes of the printed circuit board of the electronic part and the terminal electrodes of the circuit board of electronic equipment, dielectric filter, dielectric duplexer, and manufacturing method of the electronic part.
One preferred embodiment of the present invention provides an electronic part comprising: a printed circuit board including a first major surface and a second major surface; a circuit element disposed on the first major surface of the printed circuit board; a terminal electrode disposed on the second major surface of the printed circuit board and including a major surface opposed to the second major surface of the printed circuit board; a soldering-resistant film disposed on the second major surface of the printed circuit board and including a major surface opposed to the second major surface of the printed circuit board; wherein the distance between the major surface of the terminal electrode and the second major surface of the printed circuit board is substantially equal to or larger than the distance between the major surface of the soldering-resistant film in the vicinity of the terminal electrode and the second major surface of the printed circuit board.
According to the above described structure and arrangement, since the allowance of warping of the printed circuit board of an electronic part increases, even if the printed circuit board is warped to some extent and the terminal electrode is deformed in the direction that the terminal electrode be lifted out of the terminal electrode of the circuit board of electronic equipment, originally there is a margin of the protrusion of the terminal electrode of the printed circuit board from the surface of the soldering-resistant film and accordingly both electrodes are made to be securely connected.
In the above described electronic part, a plurality of coaxial dielectric resonators may be provided as the circuit element, and a signal input-output terminal maybe provided as the terminal electrode thereby constituting a dielectric filter. Further, at least two of the dielectric filters may be provided on the printed circuit board thereby constituting a dielectric duplexer.
Particularly in the construction where coaxial dielectric resonators having a relatively large occupied space to the area of the printed circuit board are mounted, the warping of the printed circuit board generally becomes large compared with electronic parts where only chip parts of small size are mounted, but according to the above arrangement the dielectric filter or dielectric duplexer is made to be securely mounted on the circuit board of electronic equipment.
Another preferred embodiment of the present invention provides a method of manufacturing an electronic part, comprising: mounting a circuit element on the first major surface of a printed circuit board; disposing a terminal electrode on the second major surface of the printed circuit board, the terminal electrode including a major surface opposed to the second major surface of the printed circuit board; disposing a soldering-resistant film on the second major surface of the printed circuit board, the soldering-resistant film including a major surface opposed to the second major surface of the printed circuit board; wherein the terminal electrode is formed by disposing an electrode film on the second major surface of the printed circuit board and etching the electrode film excluding the portion of the terminal electrode; the soldering-resistant film is disposed on the etched portion of the electrode film; and the distance between the major surface of the terminal electrode and the second major surface of the printed circuit board is made substantially equal to or larger than the distance between the major surface of the soldering-resistant film in the vicinity of the terminal electrode and the second major surface of the printed circuit board.
According to the above described method, the surface of a terminal electrode can be highly precisely protruded by etching so as to have the above described distance, and the manufacturing is made easy.
Yet another preferred embodiment of the present invention provides a method of manufacturing an electronic part, comprising: mounting a circuit element on the first major surface of a printed circuit board; disposing a terminal electrode on the second major surface of the printed circuit board, the terminal electrode including a major surface opposed to the second major surface of the printed circuit board; disposing a soldering-resistant film on the second major surface of the printed circuit board, the soldering-resistant film including a major surface opposed to the second major surface of the printed circuit board; wherein the terminal electrode is formed by disposing an electrode film on the second major surface of the printed circuit board and plating the electrode film at the portion of the terminal electrode; the soldering-resistant film is disposed on the electrode film excluding the portion of the terminal electrode; and the distance between the major surface of the terminal electrode and the second major surface of the printed circuit board is made substantially equal to or larger than the distance between the major surface of the soldering-resistant film in the vicinity of the terminal electrode and the second major surface of the printed circuit board.
According to the above described method, the surface of a terminal electrode can be highly precisely protruded by plating so as to have the above described distance.
Other features and advantages of the present invention will become apparent from the following description of the invention which refers to the accompanying drawings.